Resolution-enhancement technologies (RET), such as optical proximity correction (OPC), are widely applied to the layouts of integrated circuits (ICs) in semiconductor fabrication processes in order to improve manufacturability and yield. Often times, different shapes of the polygons in the IC layout require different types or degrees of OPC. Therefore, OPC involves identifying certain shapes and fragments in the polygons of the IC layouts, and applying the appropriate type and degree of OPC to the identified shapes.
In order to identify shapes in the IC layouts, conventional OPC systems define shapes with rigid rules indicating how the edges in the defined shape are connected to each other. These rules also define what the length of the edges should be and what angle the edges should form. However, the rigid shape definitions in conventional OPC systems have the disadvantage that even a minor variation of a certain shape has to be defined as another new shape, because the rigid shape definitions do not accommodate variations of the defined shapes. Thus, the conventional OPC systems require a number of shape definitions corresponding to many of the possible variations of the shapes of the polygons in an IC layout. This is very inconvenient and cumbersome. Even then, it is almost impossible to contemplate and define every type of shape that may exist in an IC layout.
Therefore, there is a need for more flexible shape definitions for use in OPC where each shape definition can cover variations of its defined shape. There is also a need for more flexible shape definitions for use in OPC where variations of a shape are also identified as having the same shape.